You have some pretty solid level design going. The use of the on/off blocks was pretty clever, mostly in the cave sub-areas, and the alligator was a great idea for the original lava enemy of Super Mario World. It was a bit long (Though, I'm not sure what world this is supposed to be in) and it took me awhile to reach the mid-way point, but I eventually got to the end. I liked how some platforms and objects were hidden behind the leaves in the dense forest areas, leaving the player to question his security on some of the bridges.
When I first played this I honestly didn't expect this thing from Cave Story to pop out when I walked to the sign, a little more clarification from the message box would be helpful.
The following is completely not your fault, but it is how the sprite is coded:
The alligator jumps out of the water and falls somewhere else, leading me to believe it's safe to swim...
But when I swim past the spot where it originally spawned, I instantly die. In the second screenshot you can see the green water it leaves behind when it jumps out, so it hasn't respawned yet. This happens in every spot where the alligator is placed, because the original sprite was meant to be put in lava, not water.
Here is another screenshot of the incident. Also in these screenshots, there is a weird water/air transition and at first I thought those blocks were solid. :/
What. I'm going to assume this is an emulation issue with ZSNES 1.51
For future reference, remember to add layer priority over Mario to the land the leaves connect to so his head doesn't poke out from behind the scenery.
On this jump, I was forced to take a hit because the alligator moves at the same time as the first one, and I can't avoid it by jumping on a vine like before.